Hello,

I switched all my fluids to synthetic the other day. No problems with the Tranny, Transfer case or front diff. Did the same on my wifes Merc with no problems at all, even the rear diff.

I have a leak in my rear diff on my pickup now. A rather fast one. I used the Permatex Form-a-gasket. I cleaned the surfaces very well....or at least I believe I did. I cleaned and lightly sanded all surfaces and cleaned again.

Directions said to put the gasket material on both the cover plate and the diff housing. I went around the bolt holes also. I may have put more on than I needed. Stuff came out rather fast. It said to let dry till tacky. Well it was over 100 degrees (yes I know I'm in Montana) and the stuff never did get tacky, even after a couple hours. I put it together anyhow and it sat for a day before I used my pickup.

We then went on a couple hundred mile road trip. When I got back the diff was leaking like a sieve. I tried tightening the bolts some more but there was no more left to tighten.

I have since drained the oil slowly out of the diff. I will strain the fluid thru a paint strainer to make sure its free of dirt. It's still clear and looks clean.

Sorry this is so long, but maybe someone can tell me what I did wrong and offer some hints as to what I can do right next time! I was told to buy the Permatex RTV Blue silicon. It says to apply to one surface only. Sound good?

I've switched to synthetics on all my vehicles and this is the first time this has ever happened. Any ideas will be appreciated.

 

I would go to the local parts store and buy a roll of 1/8" or 3/32" gasket material. Make sure you get the grey, not the cork. It should be about 12" x 4' roll for less than $5.00. Take your diff cover and mark the outer edge and the bolt holes. Use a sharp knife to cut it out and then cut out the middle part. Apply Blue RTV to the housing, put gasket in place, and then cover. Tighten bolts until blue RTV starts to squeeze out. Let it sit 4-6 hours and you should be good. I've used that method many times without any problems. This will allow you to tighten the bolts a little more if it does begin to leak. I know books say to use sealer only, but there is nothing wrong with using 1/8" gasket material.

 

You dont want to use a solid gasket.....I use the red RTV on my jeep....never had a problem.

The reason your diff is leaking is because you overtightened the diff cover bolts. They have a specific torque (look in your manual) and it is usually fairly small. Remember that you used a "liquid" gasket and overtightening the bolts will just squeeze out all the RTV.

Pull the cover....scrape the old junk off....apply the RTV...let it sit for a few....apply the cover to the axle and tighten the bolts to finger tight...using a torque wrench, tighten to proper torque. Refill (Slowly as not to overfill) the diff.

 

Thanks Guys,

Any idea what the torgue is on the Diff Cover bolts?

 

It should be around 30 ft-lbs.....well....at least that is what it is on my jeep.

 

The most common problem when the cover leaks is that it wasnt cleaned properly. Oil stays in the bottom bolt holes and then oozes out when you put the bolts in. Clean the cover and housing spotlessly clean with brake cleaner and blow out the bolt holes. Use good quality (probably Permatex) automotive silicone, red, blue, black doesnt really matter on the cover as it doesnt get very hot. Let the silicone set up a while before refilling the diff. BTW the easiest way to fill the diff is to remove the VSS from the top of the housing and pour it in through there.

 

Too bad you probably already had synthetic in the rear! But it doesn't hurt anything but the wallet to freshen it up!

Dave, I assume you still take out the normal fill plug so you know when its full.

 

Yup that's right.